The present invention relates generally to the field of dynamoelectric machines, and more particularly, to an improved rotating rectifier module for use therein.
A rotating rectifier assembly is an electronic device for rectifying alternating current into direct current on rotating elements of electrical machinery. A common application of the rotating rectifier assembly is in a brushless generator.
A typical brushless generator includes an exciter and a main generator for converting the rotational energy generated by a prime mover into a multiphase alternating current (AC) power. The exciter may include stationary field windings, which when electrically coupled to receive a direct current (DC) voltage from a DC voltage source, such as a voltage regulator, voltage control device, or battery, will develop a magnetic field. The exciter may also include windings mounted on the generator rotor, which rotate within this magnetic field. During rotation, alternating current is induced in the exciter rotor windings. Typically, the exciter rotor windings are wound such that the induced alternating current is a three-phase alternating current. Rectifier circuits then rectify a three-phase AC voltage from the exciter rotor windings into a DC current output for supply to the main generator.
Because these rectifier circuits are electrically coupled between two sets of windings both mounted on the generator rotor, the rectifier circuits are likewise carried by the generator rotor—thus the term “rotating rectifier circuits.” Traditional rotating circuits include mass heavy electronic components radially mounted in a plane normal to the shaft axis. These components are caused to rotate with the shaft and are mechanically and thermally weakened by the centripetal stresses caused by this rotation.
A second problem with traditional rotating rectifier circuits is that they are not designed to be balanced in weight in the plane normal to the shaft axis. This imbalance results in eccentricities that contribute to limiting speeds of the rotating equipment to which they are applied.
Traditional rotating rectifier circuits are assembled by hand while the rotating equipment to which they are applied is also assembled. To simplify this hand assembly process, “flying leads” are used to connect the rotating rectifier circuits to the rotor windings of the exciter and the main generator. These flying leads are subject to poor electrical contact from handling and suffer from rotational stresses.
The semiconductor devices used in the rectifiers dissipate power in the form of heat during their use. Without proper attention to cooling, the semiconductor devices will fail. However, traditional rotating rectifiers lack adequate mounting surface and heat sink area to be utilized in high temperature applications.
Accordingly, a need exists for a rotating rectifier assembly that overcomes these problems with prior art designs.